Electrically-heated kiln



Oct. 9, 1928. 1,687,025

G. KELLER ELECTRICALLY HEATED KILN Filed Dec. 13, 1926' Patented Qct. 9,19 28.

UNITED STATES PATENT OFFICE.

eorrman KELLER, or entree, swirznnmivn, Assren'on ro axrrnnonsmscmr :Bnown aovnnr .1; cm, or BADEN, swrrznnnann, A JorNr-srocx comm or SWITZERLAND.

ELECTRICALLY-HEATED KILN.

Application filed December 13, 1926,-Seria1 No 154,448, and in Germany January 6, 191t8.

1o burning avoided.

Another "object is the provision of a construction which will contribute to uniformity in the heating of the material subjected to the process, for the purpose of preventing the occurrence of unburned or insufliciently burned material in, the product.

Another object is the provision of a construction adapted-for continuous operation by virtue of the fact that/the material is assed through the kiln, new raw material eing supplied as burned material is withdrawn, withoutrequiring any cessation of the burning.

Another object is the provision of a construction which will facilitate and the feeding of the charge through t e kiln.

Other and further objects will be pointed out or indicated hereinatter-or will appear to one skilled in the art upon an understanding of the invention or its employment in practice. I

In the accompan ing drawing forming a part of this speci cation, I illustrate one structural embodiment of the invention, but

the same is presented for illustration only and is not to be accorded any interpretation having the effect of limiting the claims short of the true and most comprehensive scope of the invention in the art.

In the drawing,.

Fig. 1 is a diagrammatic illustration'in the nature of a part sectional elevation of a kiln suitable for lime burning and containfeatures of my invention;

ig. 2 is a diagrammatic illustration in the nature of a cross section of same on sub' stantially line 2 2 of Fig. 1; and 7 Fig. 3 is a detail in the nature of a transverse sectional view of one of the-heaters.

In the treatmentof various materials, such as the burning of limestone or other natural forms of calcium carbonate for the production of quicklime, a uniform heating of the pieces of the raw material is of utmost imremote portance, if a good and uniform qualityof product is to be obtained. For a pure product, it-is important to avoid the smoking of the material, as from the smokeof the heat ing fuel. Likewise, the temperature should ioerkept as low as ossible, consistent with the carrying on of th as high temperatures cause impurities in the limestone to interact with'the quicklime formed, producing fusible silicates, which fill the pores, and interfere with the subsequent slaking with water or other contemplated treatments of the lime. Local underheating will result. in unconvertedlimestone in" the product. 7 V

The present invention makes-provision or e necessary combustion,v

the necesary heating of the raw material by H electrical means to a temperature whereat the combustion proceeds at a sufiiciently rapid rate, the burned product being withdrawn at the bottom of the kiln and the raw'material supplied at the top, the burn ing taking place as the material passes through'the kiln, so that the operation of the installation may be carried on continuously. The heating elements are disposed in the path of the material in a distributed arrangement,-so that the material passes into trates the organization" of a construction suitable for the burning of limestone or the like into quicklime.

'fractory walls 10 afiording the interior burning chamber 11 into which the material is charged at the top. The charge is supported on a grate 12 afiording passage therethrough for the burned material, which drops into the pit 14 and may be withdrawn through the wall opening 15. A number of heating elements 16 aresupported on the Walls in spaced relationship. and extend across the chamber 11. These heating elements are in the nature of hollow bars of a strong heat resisting and non-oxidizing metal, and contain the electrical resistance The kiln is in the nature of a hollow tower having the re elements 17 having electrical insulating" coverings 18. Suitable electrical connections heating members 16. chamber 11 through the sired, through the walls above the grate,- in quantities requisite for the combustion of the material, and the carbon dioxide and unof the chamber 11. They may be placed at different levelsv and extend in crossing directions, as illustrated.

In operation, the res1stance elements are supplied with the necessary electric currentto develop the desired degree of heat, which 7 'means providing a vertically-disposed heatis imparted to the fragmentary material in the chamber 11 throu h the walls of the grate and, if de-- reduced gases pass out of the chamber at the top. As the fragmentary material burns, it becomes'friable and breaks up and is passed through thegrate into thecpit 14, so that the charge gradually feeds down: wardly through the chamber 11 and through the heated zone or zones produced 10, the heating members. Due to the distri uted arrangement of the heating members, the material of the charge, incident to its progressive feed by gravity, is given a uniform heatin to the desired reaction temperature, with the result that a uniform product re- Kir is supplied to the- Inasmuch as the temperature of the -heating members may be definitely .con-

supported in spaced relation with respect to each other in such manner as to provide for retarded gravity-induced movement of material in said chamber, and heating means disposed within said elements and sealed thereby against direct contact with said material.

2. In apparatus of-the character described,

ing chamber, elongated hollow substantially horizontally disposed heat-radiating elements having an upwardly tapered-transverse section and supported within said chamber in spaced relation with respect to.

each other .in such manner as to provide for. retarded gravity-induced movement of material'in said chamber, the lower enlarged edges of said elements providing with the walls oflsaid chamber a pivotal support for said elementspermitting of rocking movement of the same, and heating means disposed within said elements and sealed thereby against direct contact with said material.

In testimony whereof I have hereunto subscribed my name at Zurich, Switzerland, this 26 day of November A. D. 1926. GOTTLIEB KELLER. 

